- £ 14
The Dent mean time clock, No. 39740, was used for automatically dropping the time-ball until June 24, when it was sent to England to have an invar pendulum fitted, and also electric contact springs for emitting 2-second signals. The Brock mean time clock was brought into use on June 25. It had recently been fitted with an invar pendulum and electric contacts for emitting 2-second, minute and hour signals. The contacts are similar to those described on page 105 of the Report of the Chief Astronomer, Canada. Some trouble has been experienced with the minute and hour contacts on account of the shape and size of the jewels, which do not admit of a clean drop off the tooth of the cam without the latter touching the contact lever, and so making a short circuit through the clock. This defect was however utilised for making the hour contact, one lever being held permanently off the cam, and the contact made by the rubbing of the end of the other contact lever against the tooth of the cam. New levers were provided for the minute contacts, with jewels projecting from their sides. The original levers were returned to England to have suitable jewels fitted, for use when necessary.
The coils of the accelerator and retarder were found to be defective. They were therefore rewound. A correction of 1 second can now be obtained in about 8 minutes, with the ten cell accumulator working through a 66 ohm resistance coil. In spite of the new invar pendulum rod, the temperature co-efficient of which was found to be nil, the rate of this clock has only been moderately good. After a steady rate for several days, relatively large variations occur for which no reason can be assigned. The clock is corrected daily by the electric regulating apparatus, and its daily rate is usually kept within 0s.5 by the addition or removal of weights from the pendulum.
Though kept stationary on a table near the sidereal Standard clock, Chronometer Kullberg No. 8546, which was purchased in 1913, has not maintained the steady rate reported last year. It varied from +0s.3 on January 20 to 2s.9 on December 26, under nearly identical conditions of temperature and barometric pressure. There appear to be fortuitous variations superposed on a "time factor".
The electric impulse dials in various parts of the building have required no adjustment.
Experiments with the electric transmitter under varying conditions of friction and impulse indicated that the pallet required to be jewelled and the bearings of the gravity arm improved, in order to obtain the best results from this type of clock.
Attempts to render the cylindrical glass cover airtight have proved unsuccessful.
Time Signals by Wireless Telegraphy.—Provision has been made on the Estimates for the purchase of apparatus for automatic emission of wireless time signals according to the International...
- £ 14
The Dent mean time clock, No. 39740, was used for automa- tically dropping the time-ball until June 24, when it was sent to England to have an invar pendulum fitted, and also electric contact springs for emitting 2-second signals. The Brock mean time clock was brought into use on June 25. It had recently been fitted with an invar pendulum and electric contacts for emitting 2-second, minute and hour signals. The contacts are similar to those described on page 105 of the Report of the Chief Astronomer, Canada. Some trouble has been experienced with the ininute and hour contacts on account of the shape and size of the jewels, which do not admit of a clean drop off the tooth of the cam without the latter touching the contact lever, and so making a short circuit through the clock. This defect was however utilised for making the hour contact, one lever being held permanently off the cam, and the contact made by the rubbing of the end of the other contact lever against the tooth of the cam. New levers were provided for the minute contacts, with jewels projecting from their sides. The original levers were returned to England to have suitable jewels fitted, for use when necessary.
The coils of the accelerator and retarder were found to be defective. They were therefore rewound. A correction of 1 second can now be obtained in about 8 minutes, with the ten cell accumu- lator working through a 66 ohm resistance coil. In spite of the new invar pendulum rod, the temperature co-efficient of which was found to be nil, the rate of this clock has only been moderately good. After a steady rate for several days, relatively large vari- ations occur for which no reason can be assigned. The clock is corrected daily by the electric regulating apparatus, and its daily rate is usually kept within 05 by the addition or removal of weights from the pendulum.
Though kept stationary on a table near the sidereal Standard clock, Chronometer Kullberg No. 8546, which was purchased in 1913, has not maintained the steady rate reported last year. It varied from +03 on January 20 to 29 on December 26, under nearly identical conditions of temperature and barometric pressure. There appear to be fortuitous variations superposed on a
time factor".
(C
The electric impulse dials in various parts of the building have required no adjustment,
Experiments with the electric transmitter under varying condi- tions of friction and impulse indicated that the pallet required to be jewelled and the bearings of the gravity arm improved, in order to obtain the best results from this type of clock.
Attempts to render the cylindrical glass cover airtight have proved unsuccessful.
Time Signals by Wireless Telegraphy.-Provision has been made on the Estimates for the purchase of apparatus for automatic emission of wireless time signals according to the International
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